Fuel injection systems are typically used to inject a fuel spray into an inlet manifold or a combustion chamber of an engine. Fuel injection systems have become the primary fuel delivery system used in automotive engines, having almost completely replaced carburetors since the late 1980s. Fuel injectors used in these fuel injection systems are generally capable of two basic functions. First, they deliver a metered amount of fuel for each inlet stroke of the engine so that a suitable air-fuel ratio can be maintained for the fuel combustion. Second they disperse the fuel to improve the efficiency of the combustion process. Conventional fuel injection systems are typically connected to a pressurized fuel supply, and the fuel can be metered into the combustion chamber by varying the time for which the injectors are open. The fuel can also be dispersed into the combustion chamber by forcing the fuel through a small orifice in the injectors.